<?php
// vim: foldmethod=marker

/* Generic exception class
 */
class OAuthException extends Exception
{
	// pass
}

class OAuthConsumer
{
	public $key;
	public $secret;


	function __construct( $key, $secret, $callback_url = NULL )
	{
		$this->key = $key;
		$this->secret = $secret;
		$this->callback_url = $callback_url;
	}


	function __toString( )
	{
		return "OAuthConsumer[key=$this->key,secret=$this->secret]";
	}
}

class OAuthToken
{
	// access tokens and request tokens
	public $key;
	public $secret;


	/**
	 * key = the token
	 * secret = the token secret
	 */
	function __construct( $key, $secret )
	{
		$this->key = $key;
		$this->secret = $secret;
	}


	/**
	 * generates the basic string serialization of a token that a server
	 * would respond to request_token and access_token calls with
	 */
	function to_string( )
	{
		return "oauth_token=" .
				OAuthUtil::urlencode_rfc3986( $this->key ) .
				"&oauth_token_secret=" .
				OAuthUtil::urlencode_rfc3986( $this->secret );
	}


	function __toString( )
	{
		return $this->to_string( );
	}
}

/**
 * A class for implementing a Signature Method
 * See section 9 ("Signing Requests") in the spec
 */
abstract class OAuthSignatureMethod
{
	/**
	 * Needs to return the name of the Signature Method (ie HMAC-SHA1)
	 * @return string
	 */
	abstract public function get_name( );


	/**
	 * Build up the signature
	 * NOTE: The output of this function MUST NOT be urlencoded.
	 * the encoding is handled in OAuthRequest when the final
	 * request is serialized
	 * @param OAuthRequest $request
	 * @param OAuthConsumer $consumer
	 * @param OAuthToken $token
	 * @return string
	 */
	abstract public function build_signature( $request, $consumer, $token );


	/**
	 * Verifies that a given signature is correct
	 * @param OAuthRequest $request
	 * @param OAuthConsumer $consumer
	 * @param OAuthToken $token
	 * @param string $signature
	 * @return bool
	 */
	public function check_signature( $request, $consumer, $token, $signature )
	{
		$built = $this->build_signature( $request, $consumer, $token );
		return $built == $signature;
	}
}

/**
 * The HMAC-SHA1 signature method uses the HMAC-SHA1 signature algorithm as defined in [RFC2104]
 * where the Signature Base String is the text and the key is the concatenated values (each first
 * encoded per Parameter Encoding) of the Consumer Secret and Token Secret, separated by an '&'
 * character (ASCII code 38) even if empty.
 *   - Chapter 9.2 ("HMAC-SHA1")
 */
class OAuthSignatureMethod_HMAC_SHA1 extends OAuthSignatureMethod
{
	function get_name( )
	{
		return "HMAC-SHA1";
	}


	public function build_signature( $request, $consumer, $token )
	{
		$base_string = $request->get_signature_base_string( );
		$request->base_string = $base_string;

		$key_parts = array(
			$consumer->secret,
			( $token ) ? $token->secret : ""
		);

		$key_parts = OAuthUtil::urlencode_rfc3986( $key_parts );
		$key = implode( '&', $key_parts );

		return base64_encode( hash_hmac( 'sha1', $base_string, $key, true ) );
	}
}

/**
 * The PLAINTEXT method does not provide any security protection and SHOULD only be used
 * over a secure channel such as HTTPS. It does not use the Signature Base String.
 *   - Chapter 9.4 ("PLAINTEXT")
 */
class OAuthSignatureMethod_PLAINTEXT extends OAuthSignatureMethod
{
	public function get_name( )
	{
		return "PLAINTEXT";
	}


	/**
	 * oauth_signature is set to the concatenated encoded values of the Consumer Secret and
	 * Token Secret, separated by a '&' character (ASCII code 38), even if either secret is
	 * empty. The result MUST be encoded again.
	 *   - Chapter 9.4.1 ("Generating Signatures")
	 *
	 * Please note that the second encoding MUST NOT happen in the SignatureMethod, as
	 * OAuthRequest handles this!
	 */
	public function build_signature( $request, $consumer, $token )
	{
		$key_parts = array(
			$consumer->secret,
			( $token ) ? $token->secret : ""
		);

		$key_parts = OAuthUtil::urlencode_rfc3986( $key_parts );
		$key = implode( '&', $key_parts );
		$request->base_string = $key;

		return $key;
	}
}

/**
 * The RSA-SHA1 signature method uses the RSASSA-PKCS1-v1_5 signature algorithm as defined in
 * [RFC3447] section 8.2 (more simply known as PKCS#1), using SHA-1 as the hash function for
 * EMSA-PKCS1-v1_5. It is assumed that the Consumer has provided its RSA public key in a
 * verified way to the Service Provider, in a manner which is beyond the scope of this
 * specification.
 *   - Chapter 9.3 ("RSA-SHA1")
 */
abstract class OAuthSignatureMethod_RSA_SHA1 extends OAuthSignatureMethod
{
	public function get_name( )
	{
		return "RSA-SHA1";
	}


	// Up to the SP to implement this lookup of keys. Possible ideas are:
	// (1) do a lookup in a table of trusted certs keyed off of consumer
	// (2) fetch via http using a url provided by the requester
	// (3) some sort of specific discovery code based on request
	//
	// Either way should return a string representation of the certificate
	protected abstract function fetch_public_cert( &$request );


	// Up to the SP to implement this lookup of keys. Possible ideas are:
	// (1) do a lookup in a table of trusted certs keyed off of consumer
	//
	// Either way should return a string representation of the certificate
	protected abstract function fetch_private_cert( &$request );


	public function build_signature( $request, $consumer, $token )
	{
		$base_string = $request->get_signature_base_string( );
		$request->base_string = $base_string;

		// Fetch the private key cert based on the request
		$cert = $this->fetch_private_cert( $request );

		// Pull the private key ID from the certificate
		$privatekeyid = openssl_get_privatekey( $cert );

		// Sign using the key
		$ok = openssl_sign( $base_string, $signature, $privatekeyid );

		// Release the key resource
		openssl_free_key( $privatekeyid );

		return base64_encode( $signature );
	}


	public function check_signature( $request, $consumer, $token, $signature )
	{
		$decoded_sig = base64_decode( $signature );

		$base_string = $request->get_signature_base_string( );

		// Fetch the public key cert based on the request
		$cert = $this->fetch_public_cert( $request );

		// Pull the public key ID from the certificate
		$publickeyid = openssl_get_publickey( $cert );

		// Check the computed signature against the one passed in the query
		$ok = openssl_verify( $base_string, $decoded_sig, $publickeyid );

		// Release the key resource
		openssl_free_key( $publickeyid );

		return $ok == 1;
	}
}

class OAuthRequest
{
	private $parameters;
	private $http_method;
	private $http_url;
	// for debug purposes
	public $base_string;
	public static $version = '1.0';
	public static $POST_INPUT = 'php://input';


	function __construct( $http_method, $http_url, $parameters = NULL )
	{
		if ( empty( $parameters ) )
		{
			$parameters = array( );
		}
		$parameters = array_merge( OAuthUtil::parse_parameters( parse_url( $http_url, PHP_URL_QUERY ) ), $parameters );
		$this->parameters = $parameters;
		$this->http_method = $http_method;
		$this->http_url = $http_url;
	}


	/**
	 * attempt to build up a request from what was passed to the server
	 */
	public static function from_request( $http_method = NULL, $http_url = NULL, $parameters = NULL )
	{
		$scheme = ( !isset( $_SERVER[ 'HTTPS' ] ) || $_SERVER[ 'HTTPS' ] != "on" )
				? 'http'
				: 'https';

		if ( empty( $http_url ) )
		{
			$http_url = $scheme .
					'://' . $_SERVER[ 'HTTP_HOST' ] .
					':' .
					$_SERVER[ 'SERVER_PORT' ] .
					$_SERVER[ 'REQUEST_URI' ];
		}

		if ( empty( $http_method ) )
		{
			$http_method = $_SERVER[ 'REQUEST_METHOD' ];
		}

		// We weren't handed any parameters, so let's find the ones relevant to
		// this request.
		// If you run XML-RPC or similar you should use this to provide your own
		// parsed parameter-list
		if ( !$parameters )
		{
			// Find request headers
			$request_headers = OAuthUtil::get_headers( );

			// Parse the query-string to find GET parameters
			$parameters = OAuthUtil::parse_parameters( $_SERVER[ 'QUERY_STRING' ] );

			// It's a POST request of the proper content-type, so parse POST
			// parameters and add those overriding any duplicates from GET
			if ( $http_method == "POST"
					&& @strstr( $request_headers[ "Content-Type" ],
								"application/x-www-form-urlencoded" )
			)
			{
				$post_data = OAuthUtil::parse_parameters(
					file_get_contents( self::$POST_INPUT )
				);
				$parameters = array_merge( $parameters, $post_data );
			}

			// We have a Authorization-header with OAuth data. Parse the header
			// and add those overriding any duplicates from GET or POST
			if ( @substr( $request_headers[ 'Authorization' ], 0, 6 ) == "OAuth " )
			{
				$header_parameters = OAuthUtil::split_header(
					$request_headers[ 'Authorization' ]
				);
				$parameters = array_merge( $parameters, $header_parameters );
			}
		}

		return new OAuthRequest( $http_method, $http_url, $parameters );
	}


	/**
	 * pretty much a helper function to set up the request
	 */
	public static function from_consumer_and_token( $consumer, $token, $http_method, $http_url, $parameters = NULL )
	{
		if ( empty( $parameters ) )
		{
			$parameters = array( );
		}
		$defaults = array( "oauth_version" => OAuthRequest::$version,
			"oauth_nonce" => OAuthRequest::generate_nonce( ),
			"oauth_timestamp" => OAuthRequest::generate_timestamp( ),
			"oauth_consumer_key" => $consumer->key );
		if ( $token )
		{
			$defaults[ 'oauth_token' ] = $token->key;
		}

		$parameters = array_merge( $defaults, $parameters );

		return new OAuthRequest( $http_method, $http_url, $parameters );
	}


	public function set_parameter( $name, $value, $allow_duplicates = true )
	{
		if ( $allow_duplicates && isset( $this->parameters[ $name ] ) )
		{
			// We have already added parameter(s) with this name, so add to the list
			if ( is_scalar( $this->parameters[ $name ] ) )
			{
				// This is the first duplicate, so transform scalar (string)
				// into an array so we can add the duplicates
				$this->parameters[ $name ] = array( $this->parameters[ $name ] );
			}

			$this->parameters[ $name ][ ] = $value;
		} else
		{
			$this->parameters[ $name ] = $value;
		}
	}


	public function get_parameter( $name )
	{
		return isset( $this->parameters[ $name ] ) ? $this->parameters[ $name ] : null;
	}


	public function get_parameters( )
	{
		return $this->parameters;
	}


	public function unset_parameter( $name )
	{
		unset( $this->parameters[ $name ] );
	}


	/**
	 * The request parameters, sorted and concatenated into a normalized string.
	 * @return string
	 */
	public function get_signable_parameters( )
	{
		// Grab all parameters
		$params = $this->parameters;

		// Remove oauth_signature if present
		// Ref: Spec: 9.1.1 ("The oauth_signature parameter MUST be excluded.")
		if ( isset( $params[ 'oauth_signature' ] ) )
		{
			unset( $params[ 'oauth_signature' ] );
		}

		return OAuthUtil::build_http_query( $params );
	}


	/**
	 * Returns the base string of this request
	 *
	 * The base string defined as the method, the url
	 * and the parameters (normalized), each urlencoded
	 * and the concated with &.
	 */
	public function get_signature_base_string( )
	{
		$parts = array(
			$this->get_normalized_http_method( ),
			$this->get_normalized_http_url( ),
			$this->get_signable_parameters( )
		);

		$parts = OAuthUtil::urlencode_rfc3986( $parts );

		return implode( '&', $parts );
	}


	/**
	 * just uppercases the http method
	 */
	public function get_normalized_http_method( )
	{
		return strtoupper( $this->http_method );
	}


	/**
	 * parses the url and rebuilds it to be
	 * scheme://host/path
	 */
	public function get_normalized_http_url( )
	{
		$parts = parse_url( $this->http_url );

		$scheme = $parts[ 'scheme' ];
		$host = $parts[ 'host' ];

		if ( !empty( $parts[ 'port' ] ) )
		{
			$port = $parts[ 'port' ];
		}
		else
		{
			$port = ( $scheme == 'https' ) ? '443' : '80';
		}

		if ( !empty( $parts[ 'path' ] ) )
		{
			$path = $parts[ 'path' ];
		}
		else
		{
			$path = '';
		}

		if ( ( $scheme == 'https' && $port != '443' )
				|| ( $scheme == 'http' && $port != '80' ) )
		{
			$host = "$host:$port";
		}
		return "$scheme://$host$path";
	}


	/**
	 * builds a url usable for a GET request
	 */
	public function to_url( )
	{
		$post_data = $this->to_postdata( );
		$out = $this->get_normalized_http_url( );
		if ( $post_data )
		{
			$out .= '?' . $post_data;
		}
		return $out;
	}


	/**
	 * builds the data one would send in a POST request
	 */
	public function to_postdata( )
	{
		return OAuthUtil::build_http_query( $this->parameters );
	}


	/**
	 * builds the Authorization: header
	 */
	public function to_header( $realm = null )
	{
		$first = true;
		if ( $realm )
		{
			$out = 'Authorization: OAuth realm="' . OAuthUtil::urlencode_rfc3986( $realm ) . '"';
			$first = false;
		} else
		{
			$out = 'Authorization: OAuth';
		}

		$total = array( );
		foreach ( $this->parameters as $k => $v )
		{
			if ( substr( $k, 0, 5 ) != "oauth" ) {
				continue;
			}
			if ( is_array( $v ) )
			{
				throw new OAuthException( 'Arrays not supported in headers' );
			}
			$out .= ( $first ) ? ' ' : ',';
			$out .= OAuthUtil::urlencode_rfc3986( $k ) .
					'="' .
					OAuthUtil::urlencode_rfc3986( $v ) .
					'"';
			$first = false;
		}
		return $out;
	}


	public function __toString( )
	{
		return $this->to_url( );
	}


	public function sign_request( $signature_method, $consumer, $token )
	{
		$this->set_parameter(
			"oauth_signature_method",
			$signature_method->get_name( ),
			false
		);
		$signature = $this->build_signature( $signature_method, $consumer, $token );
		$this->set_parameter( "oauth_signature", $signature, false );
	}


	public function build_signature( $signature_method, $consumer, $token )
	{
		$signature = $signature_method->build_signature( $this, $consumer, $token );
		return $signature;
	}


	/**
	 * util function: current timestamp
	 */
	private static function generate_timestamp( )
	{
		return time( );
	}


	/**
	 * util function: current nonce
	 */
	private static function generate_nonce( )
	{
		$mt = microtime( );
		$rand = mt_rand( );

		return md5( $mt . $rand ); // md5s look nicer than numbers
	}
}

class OAuthServer
{
	protected $timestamp_threshold = 300; // in seconds, five minutes
	protected $version = '1.0'; // hi blaine
	protected $signature_methods = array( );

	protected $data_store;


	function __construct( $data_store )
	{
		$this->data_store = $data_store;
	}


	public function add_signature_method( $signature_method )
	{
		$this->signature_methods[ $signature_method->get_name( ) ] =
				$signature_method;
	}


	// high level functions

	/**
	 * process a request_token request
	 * returns the request token on success
	 */
	public function fetch_request_token( &$request )
	{
		$this->get_version( $request );

		$consumer = $this->get_consumer( $request );

		// no token required for the initial token request
		$token = NULL;

		$this->check_signature( $request, $consumer, $token );

		// Rev A change
		$callback = $request->get_parameter( 'oauth_callback' );
		$new_token = $this->data_store->new_request_token( $consumer, $callback );

		return $new_token;
	}


	/**
	 * process an access_token request
	 * returns the access token on success
	 */
	public function fetch_access_token( &$request )
	{
		$this->get_version( $request );

		$consumer = $this->get_consumer( $request );

		// requires authorized request token
		$token = $this->get_token( $request, $consumer, "request" );

		$this->check_signature( $request, $consumer, $token );

		// Rev A change
		$verifier = $request->get_parameter( 'oauth_verifier' );
		$new_token = $this->data_store->new_access_token( $token, $consumer, $verifier );

		return $new_token;
	}


	/**
	 * verify an api call, checks all the parameters
	 */
	public function verify_request( &$request )
	{
		$this->get_version( $request );
		$consumer = $this->get_consumer( $request );
		$token = $this->get_token( $request, $consumer, "access" );
		$this->check_signature( $request, $consumer, $token );
		return array( $consumer, $token );
	}


	// Internals from here
	/**
	 * version 1
	 */
	private function get_version( &$request )
	{
		$version = $request->get_parameter( "oauth_version" );
		if ( !$version )
		{
			// Service Providers MUST assume the protocol version to be 1.0 if this parameter is not present.
			// Chapter 7.0 ("Accessing Protected Ressources")
			$version = '1.0';
		}
		if ( $version !== $this->version )
		{
			throw new OAuthException( "OAuth version '$version' not supported" );
		}
		return $version;
	}


	/**
	 * figure out the signature with some defaults
	 */
	private function get_signature_method( &$request )
	{
		$signature_method =
				@$request->get_parameter( "oauth_signature_method" );

		if ( !$signature_method )
		{
			// According to chapter 7 ("Accessing Protected Ressources") the signature-method
			// parameter is required, and we can't just fallback to PLAINTEXT
			throw new OAuthException( 'No signature method parameter. This parameter is required' );
		}

		if ( !in_array( $signature_method,
						array_keys( $this->signature_methods ) ) )
		{
			throw new OAuthException(
				"Signature method '$signature_method' not supported " .
						"try one of the following: " .
						implode( ", ", array_keys( $this->signature_methods ) )
			);
		}
		return $this->signature_methods[ $signature_method ];
	}


	/**
	 * try to find the consumer for the provided request's consumer key
	 */
	private function get_consumer( &$request )
	{
		$consumer_key = @$request->get_parameter( "oauth_consumer_key" );
		if ( !$consumer_key )
		{
			throw new OAuthException( "Invalid consumer key" );
		}

		$consumer = $this->data_store->lookup_consumer( $consumer_key );
		if ( !$consumer )
		{
			throw new OAuthException( "Invalid consumer" );
		}

		return $consumer;
	}


	/**
	 * try to find the token for the provided request's token key
	 */
	private function get_token( &$request, $consumer, $token_type = "access" )
	{
		$token_field = @$request->get_parameter( 'oauth_token' );
		$token = $this->data_store->lookup_token(
			$consumer, $token_type, $token_field
		);
		if ( !$token )
		{
			throw new OAuthException( "Invalid $token_type token: $token_field" );
		}
		return $token;
	}


	/**
	 * all-in-one function to check the signature on a request
	 * should guess the signature method appropriately
	 */
	private function check_signature( &$request, $consumer, $token )
	{
		// this should probably be in a different method
		$timestamp = @$request->get_parameter( 'oauth_timestamp' );
		$nonce = @$request->get_parameter( 'oauth_nonce' );

		$this->check_timestamp( $timestamp );
		$this->check_nonce( $consumer, $token, $nonce, $timestamp );

		$signature_method = $this->get_signature_method( $request );

		$signature = $request->get_parameter( 'oauth_signature' );
		$valid_sig = $signature_method->check_signature(
			$request,
			$consumer,
			$token,
			$signature
		);

		if ( !$valid_sig )
		{
			throw new OAuthException( "Invalid signature" );
		}
	}


	/**
	 * check that the timestamp is new enough
	 */
	private function check_timestamp( $timestamp )
	{
		if ( !$timestamp )
		{
			throw new OAuthException(
				'Missing timestamp parameter. The parameter is required'
			);
		}

		// verify that timestamp is recentish
		$now = time( );
		if ( abs( $now - $timestamp ) > $this->timestamp_threshold )
		{
			throw new OAuthException(
				"Expired timestamp, yours $timestamp, ours $now"
			);
		}
	}


	/**
	 * check that the nonce is not repeated
	 */
	private function check_nonce( $consumer, $token, $nonce, $timestamp )
	{
		if ( !$nonce )
		{
			throw new OAuthException(
				'Missing nonce parameter. The parameter is required'
			);
		}

		// verify that the nonce is uniqueish
		$found = $this->data_store->lookup_nonce(
			$consumer,
			$token,
			$nonce,
			$timestamp
		);
		if ( $found )
		{
			throw new OAuthException( "Nonce already used: $nonce" );
		}
	}
}

class OAuthDataStore
{
	function lookup_consumer( $consumer_key )
	{
		// implement me
	}


	function lookup_token( $consumer, $token_type, $token )
	{
		// implement me
	}


	function lookup_nonce( $consumer, $token, $nonce, $timestamp )
	{
		// implement me
	}


	function new_request_token( $consumer, $callback = null )
	{
		// return a new token attached to this consumer
	}


	function new_access_token( $token, $consumer, $verifier = null )
	{
		// return a new access token attached to this consumer
		// for the user associated with this token if the request token
		// is authorized
		// should also invalidate the request token
	}
}

class OAuthUtil
{
	public static function urlencode_rfc3986( $input )
	{
		if ( is_array( $input ) )
		{
			return array_map( array( 'OAuthUtil', 'urlencode_rfc3986' ), $input );
		} else {
			if ( is_scalar( $input ) )
			{
				return str_replace(
					'+',
					' ',
					str_replace( '%7E', '~', rawurlencode( $input ) )
				);
			} else
			{
				return '';
			}
		}
	}


	// This decode function isn't taking into consideration the above
	// modifications to the encoding process. However, this method doesn't
	// seem to be used anywhere so leaving it as is.
	public static function urldecode_rfc3986( $string )
	{
		return urldecode( $string );
	}


	// Utility function for turning the Authorization: header into
	// parameters, has to do some unescaping
	// Can filter out any non-oauth parameters if needed (default behaviour)
	public static function split_header( $header, $only_allow_oauth_parameters = true )
	{
		$pattern = '/(([-_a-z]*)=("([^"]*)"|([^,]*)),?)/';
		$offset = 0;
		$params = array( );
		while ( preg_match( $pattern, $header, $matches, PREG_OFFSET_CAPTURE, $offset ) > 0 )
		{
			$match = $matches[ 0 ];
			$header_name = $matches[ 2 ][ 0 ];
			$header_content = ( isset( $matches[ 5 ] ) ) ? $matches[ 5 ][ 0 ] : $matches[ 4 ][ 0 ];
			if ( preg_match( '/^oauth_/', $header_name ) || !$only_allow_oauth_parameters )
			{
				$params[ $header_name ] = OAuthUtil::urldecode_rfc3986( $header_content );
			}
			$offset = $match[ 1 ] + strlen( $match[ 0 ] );
		}

		if ( isset( $params[ 'realm' ] ) )
		{
			unset( $params[ 'realm' ] );
		}

		return $params;
	}


	// helper to try to sort out headers for people who aren't running apache
	public static function get_headers( )
	{
		if ( function_exists( 'apache_request_headers' ) )
		{
			// we need this to get the actual Authorization: header
			// because apache tends to tell us it doesn't exist
			$headers = apache_request_headers( );

			// sanitize the output of apache_request_headers because
			// we always want the keys to be Cased-Like-This and arh()
			// returns the headers in the same case as they are in the
			// request
			$out = array( );
			foreach ( $headers AS $key => $value )
			{
				$key = str_replace(
					" ",
					"-",
					ucwords( strtolower( str_replace( "-", " ", $key ) ) )
				);
				$out[ $key ] = $value;
			}
		} else
		{
			// otherwise we don't have apache and are just going to have to hope
			// that $_SERVER actually contains what we need
			$out = array( );
			if ( isset( $_SERVER[ 'CONTENT_TYPE' ] ) )
			{
				$out[ 'Content-Type' ] = $_SERVER[ 'CONTENT_TYPE' ];
			}
			if ( isset( $_ENV[ 'CONTENT_TYPE' ] ) )
			{
				$out[ 'Content-Type' ] = $_ENV[ 'CONTENT_TYPE' ];
			}

			foreach ( $_SERVER as $key => $value )
			{
				if ( substr( $key, 0, 5 ) == "HTTP_" )
				{
					// this is chaos, basically it is just there to capitalize the first
					// letter of every word that is not an initial HTTP and strip HTTP
					// code from przemek
					$key = str_replace(
						" ",
						"-",
						ucwords( strtolower( str_replace( "_", " ", substr( $key, 5 ) ) ) )
					);
					$out[ $key ] = $value;
				}
			}
		}
		return $out;
	}


	// This function takes a input like a=b&a=c&d=e and returns the parsed
	// parameters like this
	// array('a' => array('b','c'), 'd' => 'e')
	public static function parse_parameters( $input )
	{
		if ( !isset( $input ) || !$input ) {
			return array( );
		}

		$pairs = explode( '&', $input );

		$parsed_parameters = array( );
		foreach ( $pairs as $pair )
		{
			$split = explode( '=', $pair, 2 );
			$parameter = OAuthUtil::urldecode_rfc3986( $split[ 0 ] );
			$value = isset( $split[ 1 ] ) ? OAuthUtil::urldecode_rfc3986( $split[ 1 ] ) : '';

			if ( isset( $parsed_parameters[ $parameter ] ) )
			{
				// We have already recieved parameter(s) with this name, so add to the list
				// of parameters with this name

				if ( is_scalar( $parsed_parameters[ $parameter ] ) )
				{
					// This is the first duplicate, so transform scalar (string) into an array
					// so we can add the duplicates
					$parsed_parameters[ $parameter ] = array( $parsed_parameters[ $parameter ] );
				}

				$parsed_parameters[ $parameter ][ ] = $value;
			} else
			{
				$parsed_parameters[ $parameter ] = $value;
			}
		}
		return $parsed_parameters;
	}


	public static function build_http_query( $params )
	{
		if ( !$params ) {
			return '';
		}

		// Urlencode both keys and values
		$keys = OAuthUtil::urlencode_rfc3986( array_keys( $params ) );
		$values = OAuthUtil::urlencode_rfc3986( array_values( $params ) );
		$params = array_combine( $keys, $values );

		// Parameters are sorted by name, using lexicographical byte value ordering.
		// Ref: Spec: 9.1.1 (1)
		uksort( $params, 'strcmp' );

		$pairs = array( );
		foreach ( $params as $parameter => $value )
		{
			if ( is_array( $value ) )
			{
				// If two or more parameters share the same name, they are sorted by their value
				// Ref: Spec: 9.1.1 (1)
				natsort( $value );
				foreach ( $value as $duplicate_value )
				{
					$pairs[ ] = $parameter . '=' . $duplicate_value;
				}
			} else
			{
				$pairs[ ] = $parameter . '=' . $value;
			}
		}
		// For each parameter, the name is separated from the corresponding value by an '=' character (ASCII code 61)
		// Each name-value pair is separated by an '&' character (ASCII code 38)
		return implode( '&', $pairs );
	}
}

?>
